The use of radio-frequency heating equipment has become quite common in industry in recent years. At the same time it is suspected that the electric and magnetic fields produced by such equipment are dangerous to people, and in particular to workers. Thus, safety regulations have been issued in a number of countries, regarding the operation of such equipment, with respect to the permissible levels of exposure. These safety regulations are not generally accepted however. Therefore, manufacturers and users of industrial radio-frequency heating equipment are not bound to comply with them to warrant low levels of field emission, either at the manufacturing stage, or in connection with maintainance procedures. On the other hand, both social and health bodies and scientific institutions are more and more frequently requested to ascertain possible dangerous conditions in the above mentioned field.
A careful survey of the conditions under which equipment is likely to create electric or magnetic fields has given following results:
The intensity of electric or magnetic fields decreases rapidly with the distance from the source; thus areas of possible risk for the workers are confined to the space immediately surrounding the source and possibly the metal structures electrically coupled to them; PA1 Generally, only electric fileds are observed close to the machines, whereas the occurrence of significant magnetic fields is less frequent; PA1 The intensity and frequency of the fields vary both in a short span of time (due to instability and to loading conditions) and over long intervals (due to aging of the equipment and due to intentional or unintentional modifications). PA1 It can be easily used, even by operators completely unaware of the problems connected with the measurement of electric and magnetic fields; PA1 It is a portable, rugged instrument relatively unaffected by variations of environmental conditions (temperature, humidity, dusts, etc.); PA1 It is a simple and low cost tool, and therefore likely to receive quite a large diffusion. A large diffusion, and hence immediate availability is essential to the satisfaction of the above outlined operating needs.
As a consequence, the control of the electric field intensity (and less frequently that of the magnetic field) carried out from time to time by highly skilled operators, with high precision equipment on one hand, cannot be easily carried out on a large scale and on the other hand the number of skilled operators available is not sufficient to give a final answer to the above mentioned concern.